Only second material in mesh renderer showing

I have an fbx model and I want to assign the material ‘USSRColour’ to it. The problem is that it only works if it has two elements in the materials array, and only the second one affects the material displayed
e.g. if the first element is any material and the second is USSRColour, it will be USSRColour; if the only element is USSRColour, it will be invisible.
I should also add that this is only a problem with this particular model. I have a few others which work fine.

This is to do with how the model was made. Normally each material "slot"is used on different parts of the model (eg one material for the head, one for the body). It could be that when the model was created, an unused material was left it place, or the first material is only used on a small part of the model that you aren’t noticing.